Denture



Patented Nov. 8, 1938 UNITED STATES PATENT OFFICE DENTURE No Drawing. Application May 14, 1934, Serial No. 725,651

3 Claims.

This invention relates to dentures, and may be characterized as an improvement upon the denture described and claimed in my copending application Serial No. 599,071, filed March 15,

5 1932, which matured into Patent No. 1,958,446,

issued May 1, 1934.

I have determined by experiment that alloys of higher tungsten and molybdenum content than specified in my above patent are practicable without impairing the characteristics and-advantageous properties of the denture of my patent, and with additional advantageous results;

I find it possible to make a highly resilient and tough alloy for the purpose described and with the characteristics and advantageous properties of the denture of my prior application by means of increasing the tungsten content instead of depending upon the carbon content for resilience, as was done in the denture of my prior application. This alloy, for the purpose of my invention, may be practically carbonless, although, as will hereinafter appear, some carbon is allowable, particularly in the lower tungsten ranges approaching the tungsten range in the denture of my prior application.

I further find it possible to make desirable denture alloys with the characteristics and advantageous properties of the denture of my prior application by increasing the molybdenum content either with or without a small percentage of carbon, and. that this increased molybdenum content gives the additional advantageous property of increased resistance to hydrochloric acid. I still further find it possible to make desirable denture alloys with the characteristics and advantageous properties of the denture of my prior application containing both tungsten and molybdenum. Dentures containing both tungsten and molybdenum have the advantage gained by using tungsten to increase the resilience, supplemented by the higher resistance to the action of hydrochloric acid as a result of the molybdenum, all without impairing the characteristics and advantageous properties of the denture of my prior application.

For a full understanding of the denture of my prior application and the characteristics and advantageous properties of the denture of that application, which characteristics and advantageous properties are preserved in the denture alloys of the present application, reference is made here to the prior application above identifled, and the disclosure of that application is hereby incorporated in this application as if forming a part hereof.

I have determined that a denture may be formed as a new article of manufacture comprising an alloy having cobalt as the principle or essential constituent and containing a combined percentage of chromium and tungsten not substantially over forty to forty-five per cent. The higher tungsten alloys in combination with chromium of about thirty per cent and pracl0 tically carbonless, have a very desirable degree of resilience, associated with toughness and the characteristics and advantageous properties of the alloy denture of my prior application. The substantially carbonless alloys of this type have 15 exhibited a resilience superior to the denture alloy of my prior application combined with a higher degree of toughness and have, at the same time, the advantageous properties of the denture alloy of my prior application. These alloys are 20 of practical value, not only for casting purposes in accordance with my prior application, but for the production of wrought wires to be used in dentistry for making clasps and the like. The carbonless, or substantially carbonless, alloys 25 have an advantage in that it is easier to maintain uniform physical characteristics, these alloys being very sensitive to the small variations in the carbon content which, in practical work, are very difficult to control. Some carbon is al- 0 lowable in the lower tungsten ranges, approaching the tungsten content of the denture alloy of my prior application without causing brittleness. And a tungsten content up to as high as twenty-five per cent is contemplated within the 35 scope of my present invention.

A composition which has exhibited excellent results on tests contained fifteen per cent tungsten, thirty per cent chromium and the remainder cobalt. It contained no carbon. 40

I have obtained advantageous results with the carbonless alloys by keeping a fairly low tungsten content of about five per cent and increasing the chromium to approximately forty per cent. The high chromium alloys, however, are noticeably more difiicult to melt, and in this respect, the high tungsten alloy above mentioned is preferable, although the low tungsten content alloy above described is contemplated as coming within the spirit andscope of my present invention.

To summarize, I have found it possible to make a highly resilient and tough alloy by means of increasing the tungsten content instead of depending upon the carbon content for resilience 55 as was done in the denture alloy of my prior application.

I have further found that the characteristics and advantageous properties of the denture alloy of my prior application may be retained and further improve results obtained by increasing the molybdenum content. It is not possible, however, to carry the molybdenum content quite as high as the tungsten content in the previously mentioned alloy. With twelve per cent molybdenum the alloy is very tough, but with twenty per cent it is decidedly brittle, this, in combination with thirty per cent chromium. It is possible to introduce carbon to the extent of about .60 into an alloy containing twelve per cent molybdenum without obtaining a brittle alloy. With respect to the tungsten alloys, some carbon is allowable in the lower tungsten ranges as already described.

To summarize, it is possible to make desirable alloys by increasing the molybdenum content, either with or without a small percentage of carbon. The molybdenum alloys have a very desirable quality in that they are more resistant to hydrochloric acid than the denture alloy of my prior application. It should be noted, however, that the addition of molybdenum in excess of twenty per cent tends toward unusable alloys, being both brittle and extremely high fusing. As an alternative for avoiding brittleness, the chromium content may be reduced.

I have further determined that some compositions containing both tungsten and molybdenum are suitable. These have desirable properties in that the advantage gained by using tungsten to increase the resilience is supplemented by the higher resistance to the action of hydrochloric acid as a result of the molybdenum content. An alloy of this kind which has been found by test to have advantageous properties contained five per cent molybdenum, five per cent tungsten, thirty per cent chromium, the balance cobalt, and practically no carbon.

I contemplate within the scope of my present invention a wire of an analysis similar to the high tungsten carbonless composition mentioned above for the purpose of making clasps and the like.

The range of carbon content determined to be permissible varies from zero, or substantially zero, with the high tungsten alloys, to a maximum or not over one per cent with the alloys containing less tungsten.

In casting a denture of the alloys specified herein, it is essential to employ a mold of high refractoriness. For this purpose, the mold and casting method of my prior application, or any other equivalent or suitable mold and casting process, may be employed. The mold and casting process more fully described in my prior application constitutes one suitable mold and casting process suitable for casting dentures of the alloys of the present application. The mold and process of my prior application are referred to herein, not for limiting the present invention to formation of the denture with this mold and process, but for adequately acquainting those skilled in the art with one suitable mold and process for casting the dentures of my present invention.

The casting investment material and process disclosed in my copending application, Serial No.

721,550, filed April 20, 1934, which matured into Patent No. 2,081,558, issued May 25, 1937, are also highly suitable and advantageous in the casting of dentures of the alloys of my present invention, and reference is hereby incorporated herein for the further details of the casting investment material and process of the last above mentioned application.

I claim:

1. As a new article of manufacture, a cast denture comprising an alloy having cobalt as the principal constituent and containing chromium from 10% up to 40% and tungsten over 5% and not exceeding 25%, said denture having the characteristic of slight shrinkage when solidifying.

2. As a new article of manufacture, a cast denture comprising an alloy having cobalt as its principal constituent and containing tungsten substantially 15% and chromium 30%, said denture having the characteristic of slight shrinkage when solidifying.

. 3; As a new article of manufacture, a cast denture comprising an alloy having cobalt as the principal constituent and containing tungsten substantially fifteen per cent, chromium substantially thirty per cent and substantially free of carbon, said denture having the characteristic of slight shrinkage when solidifying.

' CHARLES H. PRANGE. 

